Fire alarm thermostatic contact



March 7, 1939. G HUNT 2,149,997

FIRE ALARM THERMOSTA'IYIC CONTACT Filed March 26, 1937 5'8 .46 /0 /4 au1 n Jilly. 0. i- HERBERT 5. HUNT 44 45 INVENTOR. 42 V l Patented Mar.7, 1939 UNITED STATES PATENT OFFICE FIRE ALARM THERMOST'ATIO CONTACTHerbert G. Hunt, New York, N. Y.

Application March 26, 1937, Serial No. 133,197

This invention relates generally to automatic 7 Claims.

heat and possesses the quality of being able to remain comparativelyunaffected by the passage of time.

Another object herein is the provision of an alarm controlling unitwhich may be quickly and easily replaced after the unit has been actedupon by heat.

Still another object of the present invention is the provision ofstructure which is constant and uniform in sensitivity and action, andwhich when actuated by the requisite amount of heat closes an electricalcircuit of very low resistance and said circuit is closed in a positivemanner.

Among the features of the invention is the inclusion of the presentdevice in the ordinary household or office annunciator systems so thatthe same electric bell, power source, and portions of the wiring may beused with a consequent reduction in installation and maintenance cost.

The present circuit closing unit permits of simple manufacture withcorresponding economies in production so that with low initial costsufficient units may be used at various points to give adequateprotection.

These objects and further features and advan tages will more fullyappear in the progress of this disclosure and as pointed out in theappended claims.

In the drawing:

Figure 1 is a front elevational view of a preferred embodiment of theinvention with the cover removed.

Figure 2 is a plan view of Figure 1 with the cover shown in centralhorizontal section.

Figure 3 is a view similar to Figure 1 with the cover in place.

Figure a is an enlarged fragmentary view of Figure 1 showing the fusiblematerial and adjacent parts.

of the cover.

Figure 7 is a schematic diagram of an electrical circuit in which thepresent invention may be utilized.

The automatic circuit closing device generally represented by numeral 10is adapted to be quickly and conveniently placed upon or removed from amounting plate therefor generally indicated by numeral H. Mounting plateIi is preferably substantially oblong in shape and is composed of anysuitable insulating material such as fibre, Bakelite, molded plastic,wax treated Wood or ceramic. Mounting plate Il may be readily affixed toany vertically disposed surface by means of flat head screws (not shown)which penetrate the countersunk orifices 12. While some deviation fromthe vertical may be permitted in the surface to which the plate H isafiixed, best operation of the device will be obtained when said surfaceis vertical as will be more fully understood below. The mounting plateII is provided with two electrical terminal screws 13 and I4 and twocircuit closing device mounting screws 15 and It. The screws :3 to l6inclusive are threadedly mounted in the front surface of the plate II inorifices ll. Screws l3 and I5 and I6 and [4 respectively areelectrically connected by short contact strips l8 and IS. The strips 18and [9 are preferably not thick and serve to conduct electricity fromthe electrical terminal screws to the mounting screws.

The device it! is built upon a base plate 20 which may be composed ofany suitable insulating material and preferably of a vulcanized sheetfibre which permits of some compressibility rather than electricalinsulating materials which are brittle. Mounted upon plate 20 is anirregularly shaped open circuit contact plate 2!, the configuration ofwhich may best be seen in Figures 1 and 2 of the accompanying drawing.Plate 2! is maintained in position upon base plate 20 by means of amachine screw 22 which is provided with a shoulder 23 and whichthreadedly engages the plate 20. The pressure exerted between shoulder23 and plate 20 by screw 22 serves to maintain the relatively stiffcontact plate 2| in operable position and plate 2| is prevented fromturning by reason of said pressureand by reason of the right angledoffset portion 24 which engages the end 25 of the base plate 20. Theinner end of contact plate 2| is provided with a right angled forwardlybent integral lug 26 which has the lower surface 2! thereof milled,chased or otherwise roughened, as will be more particularly set forthbelow. Mounted on the opposite end of plate 20 is an irregularly shapedcircuit closing contact plate 28 which is secured in place by a machinescrew 29 which threadedly engages the plate 20. Plate 28 is preventedfrom becoming displaced under operating conditions by reason of theright angled oifset portion 30 which engages the end 3! of plate 20. Theinner end of plate 28 is provided with .a forwardly bent integral rightangle electrical contact point 32.

Pivotally mounted on the shoulder 23 of screw 22 is a contact lever 33,the configuration of which is best seen in Figures 1 and 2. The inner orfree end 34 of lever 33 is angularly disposed With relation to saidlever whereby when the lever is in its upper position, that is, when theend 34 contacts the lug 26, a uniform contact is secured over the entiresurface of said lug. End 3G is milled, chased or otherwise roughened onthe upper surface thereof so that the fusible material 35 is providedwith sufficient surface irregularities to which it may adhere. A cover36 is shaped as shown in Figure 6 and is provided with large tabs 3'!and small tabs 38. As viewed in Figure 6, the tabs 3? and 38 aresubsequently bent at right angles to the rear so that the inner surfacesadjacent the outer margins on tabs 3? will lie on the longitudinal edgesof the plate 20, as best seen in Figure 5. The cover 36 is secured inplace by crimping the same into said edges. The tabs 33 serve to almostcompletely close the ends of said cover so that dust and moisture areprevented from entering the device ill, thereby pro;- longing theefficiency thereof.

Operation The device Ill is placed upon the mounting plate H byinserting the left end thereof (as viewed on Figure 1) under the screw land then lowering the right end thereof down under the screw l6. It maybe noted at this point that owing to the irregular dispersement of thescrews l3, l5, l6 and 14 it is impossible to install the device Ill inan upside-down position so that it would then not operate. The outerterminals of the plates 2| and 28 are also suitably cut away as shown at39 and 50 so that it is a simple matter to connect conducting wires tothe screws 13 and Hi without being affected by whether or not the deviceIll is in place. When suitable connections have beenv made connectingthe device in series with a source of electrical energy and anelectrically operated annunciator, the device acts as a fire alarm. Thefusible material 35 is preferably composed of wax or pitch of such aquality that the same will lose its adhesive qualities or will fuse orflow at a predetermined temperature, as for example 110 degrees. Whensuch a temperature is reached the lever 33 falls by the action ofgravity away from the lug 26 until the lever contacts the point 32 andassumes the position indicated by the dot-dash lines on Figure 1. Inthis position the circuit is completed via screw l3, contact strip l8,screw l5, plate 2|, screw 22, lever 33, point 32, plate 28, screw it,contact strip I9 and screw 14. The lever 33 is preferably quite heavy(five ounces has been found satisfactory where the area of lug 26 isabout onequarter inch square but these constants may be varied withchanges in the composition of the fusible material 35 or changes insizes of the various parts). After the device has been acted upon byheat it is a simple procedure for anyone comparatively unskilled toloosen the screws l5 and I6 and replace a similar device at low cost.

In the circuit shown at Figure 7 there is illustrated a method by whichan ordinary house annunciator system may be used as a fire alarm system.In this figure the electric bell M is connected in series with thebattery 42 and the push button 43 by means of conductors 44 and 45.

Devices II] are connected by means of auxiliary conductors 46 and 4'! inparallel with the push button 43 and these devices Ill are placed in anylocations which are considered desirable or where a fire is more likelyto occur. While only two devices H) are indicated in this diagram, it isobvious that any number may be used where desired and a fire at anypoint will cause the device to operate, close the circuit and start thebell 4i ringing.

I wish it distinctly understood that minor changes in the materials,composition, size, shape and arrangement of the parts herein may beutilized without departing from the scope of the invention or from thespirit of the appended claims.

I claim:

1. A thermoswitch comprising: a base plate; an open circuit contactplate having an offset portion engaging an end of said base plate andhaving a right angled forwardly bent rigid integral lug; a circuitclosing contact plate mounted upon said base plate and insulated fromthe open circuit contact plate and having an offset portion engaginganother end of said base plate and having a right angled forwardly bentintegral electrical contact point; means attaching the open circuitcontact plate to the base plate; a contact lever pivotally mounted onsaid means; fusible material disposed. between the free end of saidlever and said lug and holding the lever and the lug together wherebyupon the fusing of said material the lever will drop by the action ofgravity and will rest upon the electrical contact point.

2. A thermoswitch comprising: a base plate; an open circuit contactplate having an oiiset portion engaging an end of said base plate andhaving a right angle forwardly bent integral lug; a circuit closingcontact plate mounted upon said base plate and insulated from the opencircuit contact plate and having an offset portion engaging the oppositeend of said base plate and having a right angled forwardly bent integralelectrical contact point; means attaching the open circuit contact plateto the base plate, said means being disposed below the integral lug onthe open circuit contact plate; a contact lever pivotally mounted onsaid means and having the upper surface of the free end thereofangularly disposed with relation to said lever whereby when the lever isin the uppermost position thereof said surface is parallel to theundersurface of the above mentioned lug; fusible material disposedbetween the free end of said lever and said lug and holding the leverand lug adhesively together, whereby upon the fusing of said materialthe lever will drop and will rest upon the contact point.

3. A thermoswitch comprising: a base plate; an open circuit contactplate having an offset portion engaging the end of said base plate andhaving a right angle forwardly bent integral lug having a roughenedlower surface; a circuit closing contact plate mounted upon said baseplate and insulated from the open circuit contact plate and having anoffset portion engaging the opposite end of said base plate and having aright angled forwardly bent integral electrical contact point; meansattaching the open circuit contact plate to the base plate, said meansbeing disposed below the integral lug on the open circuit contact plate;a contact lever pivotally mounted on said means and having an uppersurface of the free end thereof angularly disposed with relation to saidlever, whereby when the lever is in the uppermost position thereof saidsurface is parallel to the undersurface of the above mentioned lug;fusible material disposed between the free end of said lever and saidlug and holding the lever and lug adhesively together, whereby upon thefusing of said material the lever will drop and will rest upon thecontact point.

4. A thermoswitch comprising: a base plate; an open circuit contactplate having an ofifset portion engaging the end of said base plate andhaving a right angle forwardly bent integral lug having a roughenedlower surface; a circuit closing contact plate mounted upon said baseplate and insulated from the open circuit contact plate and having anoffset portion engaging the opposite end of said base plate and having aright angled forwardly bent in tegral electrical contact point; meansattaching the open circuit contact plate to the base plate, said meansbeing disposed below the integral lug on the open circuit contact plate;a contact lever pivotally mounted on said means and having an uppersurface of the free end thereof angularly disposed with relation to saidlever, whereby when the lever is in the uppermost position thereof saidsurface is parallel to the undersurface of the above mentioned lug, saidangularly disposed upper surface on said lever being roughened; fusiblematerial disposed between the free end of said lever and said lug andholding the lever and lug adhesively together, whereby upon the fusingof said material the lever will drop and will rest upon the contactpoint.

5. A thermoswitch comprising: an insulating base plate; an open circuitcontact plate having an offset portion engaging an end of said baseplate and extending outwardly to form an integral mounting lug, saidopen circuit contact plate having at the inner end thereof a right angleforwardly bent rigid integral tab; a circuit closing contact platemounted upon said base plate and insulated from the open circuit contactplate and having an offset portion engaging the opposite end of saidbase plate and extending outwardly to form a second integral mountinglug, said circuit closing contact plate having a right angle forwardlybent integral electrical contact point; means attaching the open circuitcontact plate to the base plate; a contact lever pivotally mounted onsaid means; fusible material disposed between the free end of said leverand said tab and holding the lever and tab together, whereby upon thefusing of said material the lever will drop and will rest upon thecontact point; and a mounting plate having thereon screws for detachablyengaging both of the said mounting lugs.

6. A thermoswitch comprising: an insulating base plate; an open circuitcontact plate having an oifset portion engaging an end of said baseplate outwardly to form an integral mounting lug, said open circuitcontact plate having at the inner end thereof a right angle forwardlybent rigid integral tab; a circuit closing contact plate mounted uponsaid base plate and insulated from the open circuit contact plate andhaving an olfset portion engaging the opposite end of said base plateextending outwardly to form a second integral mountinglug, said circuitclosing contact plate having a right angle forwardly bent integralelectrical contact point; means attaching the open circuit contact plateto the base plate; a contact lever pivotally mounted on said means forrotation about a horizontal axis; fusible material disposed between thefree end of said lever and said tab and holding the lever and tabtogether, whereby upon the fusing of said material the lever will dropand will rest upon the contact point; a mounting plate having adjacentone end thereof two projections with a predetermined spacingtherebetween and at the opposite end thereof two more projections havinga predetermined spacing therebetween which is less than the spacingexisting between the first mentioned projections; said mounting lugshaving cut out slots adapted to engage the said projections, whereby thebase plate may be installed upon the mounting plate in only oneposition.

'7. A thermal switch comprising; a vertically disposed base plate; ahorizontally elongated open circuit contact plate mounted on said baseplate in fixed relation thereto and having adjacent one end a forwardlybent rigid integral lug; an elongated contact lever; means pivotallyconnecting said lever to said contact plate adjacent the end of thelatter remote from said lug, said lever having its free end extendingbeneath said lug; fusible material connecting said lug to, andsupporting the free end of said lever; and a horizontally elongatedcircuit closing contact plate mounted upon said base plate in fixedrelation thereto and beneath and insulated from said open circuitcontact plate and having a forwardly bent integral electrical contactpoint adjacent one end and horizontally intermediate said lug and saidmeans and nearer to the latter than to said lug, and adapted upon thefusing of said fusible material and the dropping 0f the lever under theaction of gravity to be engaged by said lever and to hold the latter ina substantially horizontal position.

HERBERT G. HUNT.

